bunnyfights
noticing nice landscape pebbles
Member since May 2022
Posts: 83
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Post by bunnyfights on May 22, 2023 17:11:04 GMT -5
Found in SW driftless Wisconsin Not attracted to a strong hard-drive magnet Heavy (did not test density) Steaks dark brown looks to have a metallic shine where streak tested Pic:
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Post by rmf on May 24, 2023 19:11:56 GMT -5
Get a piece of white bathroom tile. Use the unglazed side. scratch the rocks in question on the unglazed side. This is called a streak test. Red streak is Hematite Black streak is Magnetite brown streak is Limonite
My guess is they are Psuedomorphs of limonite after pyrite/marcasite.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on May 27, 2023 17:42:42 GMT -5
SW driftless WI? that's a big area. At least a County would be helpful. If you can chip off a bit of either botyroidal piece and get a photo of a fresh surface that could be very helpful, and then try another streak test with the fresh area. At one point there were many Lead and Zinc mines in SW WI.
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bunnyfights
noticing nice landscape pebbles
Member since May 2022
Posts: 83
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Post by bunnyfights on May 28, 2023 12:34:49 GMT -5
The County is Iowa and there are no Zink or Lead mines in the general area that I am aware of. After reading up, I don't think this material is Limonite. A robust streak test shows more reddish brown then yellow brown. Additionally, a density tests result in a 5-5.5 range. I went back out and located more like items. These are all surface finds, no digging of any kind. Not sure if this matters, the area where these items were found also contains lots of petrified coral. The coral looks to be mostly made up of Stromatolite. Pick of the streak test. Center streak under the wording was done on a fresh breakage area. Here are some of the finds. I prob have 40 lbs of this material. Examples of the petrified coral I believe to be Stromatolite:
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on May 28, 2023 17:34:06 GMT -5
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Post by rmf on May 29, 2023 19:55:18 GMT -5
bunnyfights Are you kidding me? Iowa County has lots of old mines. Dodgeville area, Highland, Mineral Point, Linden,Rewey, Mifflin all mining towns. Thems is my old stompin grounds. The streak says hematite. I would say alter after Pyrite.
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bunnyfights
noticing nice landscape pebbles
Member since May 2022
Posts: 83
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Post by bunnyfights on May 30, 2023 12:12:03 GMT -5
rmf I am not kidding, I did state "general area" which is meant to communicate that these items were not a product of mine tailings.
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bunnyfights
noticing nice landscape pebbles
Member since May 2022
Posts: 83
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Post by bunnyfights on May 30, 2023 12:14:01 GMT -5
fuss Here is fracture face as you requested:
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Post by youp50 on Jun 20, 2023 21:11:45 GMT -5
I sure wish I had read this earlier or paid more attention today. We made an annual visit to the Mineral Museum. (Grandkids can do that for you)
There are some interesting pieces in the Seaman Museum on the campus of Michigan Technological University, one of which is big as a large Ottoman and you are encouraged to touch it. It is iron ore oxide that was dissolved in water and dripped onto the floor of a cavern. Much like stalagmites of limestone in other caverns. As I recall, it was difficult to process, being an oxide. The mineralogical name was never close to being filed and the miners had an interesting colloquial name for it, not filed either.
I would highly recommend a weekend trip to Houghton to visit the mineral museum. $8 for a two day pass, can't beat that. And way too much information for a single day.
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